In an inspection of defects of patterns formed on a photomask (hereinafter, also simply “mask”) to be used for photolithography, an automatic alignment method of automatically aligning a mask that is loaded onto a stage having an XY plane on which the mask can be placed, so as not to have an inclination with respect to an X direction or a Y direction being movement directions of the stage before starting the inspection has been adopted. In the conventional automatic alignment method, a specific pattern such as a cross shape is previously formed on an inspection region of a mask for automatic alignment and the specific pattern is detected from a high-magnification image obtained by imaging the mask at a high magnification. Automatic alignment is then performed by rotating the stage along with the mask on the basis of the detected specific pattern so as to eliminate an inclination of the mask with respect to a movement direction of the stage along stripes that are obtained by virtually dividing the mask inspection region on which defects of patterns are to be inspected into a plurality of strip shapes.